Piping systems, including piping systems comprising concrete pipe, have been used to supply and dispose of water, sewage, and similar fluids. The pipe may be of steel, concrete, or other construction materials. Such piping systems are typically buried underground and may traverse many miles. Accordingly, it is important to prevent the leakage of fluids from the pipe. In many instances, fluid is pumped through the pipe, therefore the pipe may be subjected to high pressures. However, even if the fluid is not pumped, it is desirable to have leak-free pipe to avoid loss or contamination of the fluid being conveyed or contamination of areas surrounding the pipe.
Piping systems are susceptible to leakage at joints when the joints are improperly assembled or adjacent sections of pipe are subjected to thrust forces that are sufficient to separate the adjacent pipe sections. These thrust forces are caused by directional changes in alignment of the pipeline, by obstructions to flow such as bulkheads or closed valves, or by changes in size of the pipe. While it is important to prevent such joint separation, it is noted that some-flexibility between adjacent pipe sections is desirable to facilitate the installation and assembly of the piping system and to accommodate minor movement of pipe sections during use. To accomplish the objective of preventing joint separation while permitting some degree of flexibility, various restrained joints have been developed. A particular type of restrained joint is disclosed in U.S. Pat. Nos. 3,177,019; 3,776,576; and 5,004,274, each assigned to the assignee of the present invention and hereby incorporated by reference in their entirety. Each of these patents disclose restrained joints wherein a steel locking ring is provided in a first pipe section and may be contracted to engage a corresponding recess formed into an adjacent pipe section. This type of pipe joint has particular advantages that facilitate the quick and efficient assembly of the joint restraining mechanism.
Because piping systems for supplying and disposing of water and other fluids are typically buried beneath the ground, it is important to ensure that the pipe joints are adequately sealed prior to restraining the joint and back-filling over the buried pipe. This is particularly important when structures such as roads or buildings will be constructed above the buried pipe prior to a pressure test of the completed pipeline. Without the ability to pressure test the seal of each joint as it is installed, testing the joint seals has included the use of feeler gauges or ultrasonic devices for checking the position of the gasket and then filling the completed pipeline with water, applying pressure and watching for a drop in pressure or other evidence of leakage. This method of verifying the joint seals results in the need to find where any indicated leakage is originating, uncovering the pipe at leakage site(s), installing the necessary leak repair procedure, and re-testing the entire line. Each of these steps can be very time consuming and expensive due to the buried condition of the line.
Another method of testing pipe joints has involved pressurizing an annular space in the pipe joint, adjacent the pipe sealing gasket, with air or water. To utilize this method, the pipe must be manufactured to have a closed annular space adjacent the sealing gasket, and a means to introduce a source of pressurized air or water. Advantageously, each joint may be tested prior to back-filling allowing any leakage of the joint seal to be detected and fixed prior to installation of the next pipe. This method may be used to test the joint between adjacent pipe sections from an access port located inside the pipe, when persons are permitted inside the pipe. When conditions prevent access of personnel inside the pipe, an access port coupled to the test section may be provided on the exterior of the pipe.
Therefore, a need has been noted for a pipe joint that both accommodates thrust forces while also providing assurance of the pressure seal integrity of each pipe joint in a pipeline prior to activation of an efficient restraining mechanism, installation of the next piece of pipe, and burying of the pipeline.